1. Field of the Invention
The present invention pertains to inertial instruments and more particularly to gyroscopes and accelerometers whose inertial members are supported by means of electric fields.
2. Description of Prior Art
The advantages of electric field suspension of inertial members for gyroscopes and accelerometers has been widely recognized over the past 15 years. By maintaining the rotating inertial member free of physical contact with its support, friction normally associated with bearings is virtually eliminated. The accuracy and the life of the inertial instrument can thus be greatly increased.
An early example of an electric field suspension for a gyroscope is illustrated by U.S. Pat. No. 3,003,356, issued in Oct. 1961 to Nordsick. Other U.S. patents illustrative of such support are U.S. Pat. Nos. 3,412,618, 3,469,457, and 3,262,327, all assigned to the present assignee.
The optimum performance of an inertial instrument employing electric field suspension can be achieved if the inertial member is a perfect sphere and if further it is maintained centered precisely at the center of the electrode support structure. In an electric support system of the type utilized in the apparatus of the present invention, the electric fields are established by a set of electrodes forming a spherical envelope about the inertial member. Three pairs of electrodes are provided, each pair being associated with one channel and being responsible for generating electric support field along one of three orthogonal axes. In the prior art electric suspension systems, the spherical inertial member is quite often displaced from the center of the spherical envelope because it has previously not been possible to accurately determine the precise center. This miscentering of the inertial member results in torques on the inertial member which produce undesired drifts.